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[1] The Nigde Massif, at the southern tip of the Central Anatolian Crystalline Complex, consists of two structural units. Foliations in the lower unit define a dome cored by migmatites. The contact between the two units bears all the elements of a ductile to brittle extensional detachment. Hence the Nigde Massif represents an extensional metamorphic core complex. Top-to-NE/ENE shearing at higher levels of the lower unit relates to displacement along the detachment. Deeper levels of the lower unit display high-temperature top-to-SSW ductile shearing. The two shearing deformations show a difference in the mean trend of stretching lineations of up to 58[degrees]. New [sup.40]Ar/[sup.39]Ar ages combined with previously published data enable us to infer that the two shears were contemporaneous. In our favored interpretation, oblique shearing in the core of the dome reflects lateral underflow, i.e., horizontal flowing of the lower crust in a direction highly oblique to the direction of extension. As a result of the interaction between lateral underflow and downdip shearing along the overlying detachment, distinct structural domains are expected to exist within the migmatitic part of the core complex, with observed counterparts in the Nigde dome. Lateral underflow may reflect 'inward' flow on the scale of the core complex. Regional-scale channel flow is an alternative that would better account for the record of non-coaxial deformation in the core of the dome. More generally, we suspect that the development of lateral underflow in a metamorphic core complex more likely reflects regional channel flow, rather than local inward flow. Citation: Gautier, P., E. Bozkurt, V. Bosse, E. Hallot, and K. Dirik (2008), Coeval extensional shearing and lateral underflow during Late Cretaceous core complex development in the Nigde Massif, Central Anatolia, Turkey, Tectonics, 27, TC1003, doi: 10.1029/2006TC002089.

We present new field evidence, geochemical and isotopic data, and age constraints on Lower Jurassic mafic rock suites within a >200-km-long curvilinear belt in the Rif orogenic belt in northern Morocco and show that these rock assemblages formed as part of the Central Atlantic Magmatic Province (CAMP). The CAMP represents a large igneous province that straddles the edges of the modern peri-Atlantic continents. It developed ~200 Ma, following the initiation of the breakup of Pangea. Main magmatic rocks in the Rif External Zone include basaltic lavas, massive dolerite, and isotropic and cumulate gabbros, all intruded by dolerite and trondhjemite dikes and sills. Available U-Pb zircon ages from dolerite, gabbro, and trondhjemite dike rocks are 200 ± 4 , 196 ± 4 , and 192 ± Ma , respectively. Based on their geochemical affinities and isotopic compositions, the analyzed rocks define basalt-dolerite and gabbro-cumulate gabbro-trondhjemite groups. The basalt-dolerite group samples are subalkaline in nature and have low TiO2 contents, whereas the gabbro-cumulate gabbro-trondhjemite group samples are alkaline and display high TiO2 values. Most samples are tholeiitic in character and show large-ion lithophile and light rare earth element enrichment and high field strength element depletion compared with normal mid-ocean ridge basalt (MORB). Samples of both groups display low 143Nd/144Nd201 Ma (0.51182–0.51262) and high 87Sr/86Sri ratios with ɛ Nd values ranging from −1.51 to +4.85. The basalt-dolerite group rocks have enriched MORB compositions, compatible with the low-Ti CAMP suites, whereas the gabbro-cumulate gabbro-trondhjemite group rocks have oceanic island basalt compositions reminiscent of high-Ti CAMP suites in other continents. Magmas of the gabbro-cumulate gabbro-trondhjemite group underwent differentiation through tholeiitic fractionation. Magmas of the rocks of both groups included melt components, originated from partial melting of a previously subduction-modified subcontinental lithospheric mantle. Our results indicate that the Early Jurassic CAMP magmatism in northern Morocco marked a major episode of continental magmatism before the opening of the Maghrebian Tethys between Africa and Iberia in the latest Jurassic. [ABSTRACT FROM AUTHOR]

Abstract: In Rogaland, South Norway, a polycyclic granulite facies metamorphic domain surrounds the late‐Sveconorwegian anorthosite–mangerite–charnockite (AMC) plutonic complex. Integrated petrology, phase equilibria modelling, monazite microchemistry, Y‐in‐monazite thermometry, and monazite U–Th–Pb geochronology in eight samples, distributed across the apparent metamorphic field gradient, imply a sequence of two successive phases of ultrahigh temperature (UHT) metamorphism in the time window between 1,050 and 910 Ma. A first long‐lived metamorphic cycle (M1) between 1,045 ± 8 and 992 ± 11 Ma is recorded by monazite in all samples. This cycle is interpreted to represent prograde clockwise P–T path involving melt production in fertile protoliths and culminating in UHT conditions of ~6 kbar and 920°C. Y‐in‐monazite thermometry, in a residual garnet‐absent sapphirine–orthopyroxene granulite, provides critical evidence for average temperature of 931 and 917°C between 1,029 ± 9 and 1,006 ± 8 Ma. Metamorphism peaked after c. 20 Ma of crustal melting and melt extraction, probably supported by a protracted asthenospheric heat source following lithospheric mantle delamination. Between 990 and 940 Ma, slow conductive cooling to 750–800°C is characterized by monazite reactivity as opposed to silicate metastability. A second incursion (M2) to UHT conditions of ~3.5–5 kbar and 900–950°C, is recorded by Y‐rich monazite at 930 ± 6 Ma in an orthopyroxene–cordierite–hercynite gneiss and by an osumilite gneiss. This M2 metamorphism, typified by osumilite paragenesis, is related to the intrusion of the AMC plutonic complex at 931 ± 2 Ma. Thermal preconditioning of the crust during the first UHT metamorphism may explain the width of the aureole of contact metamorphism c. 75 Ma later, and also the rarity of osumilite‐bearing assemblages in general. [ABSTRACT FROM AUTHOR]